Neither of those are going to make a grinding noise. The upper strut mounts can cause an intermittent clunking noise over bumpy roads or when turning but not a constant noise.
If your mechanic can't find the true cause of the noise, try jacking the front tires off the ground, then running it in gear and listening by each wheel. Also see if the noise occurs when you just turn each wheel by hand. If you can't hear it that way, there is a tool called the "Chassis Ear" that will help. It's a set of six microphones, a switch box, and headphones. You clip the microphones to suspect parts, then switch between them while listening during a test drive. You might find that tool at an auto parts store that borrows or rents tools.
Front wheel bearings can become noisy too. It's very common for them to sound like an airplane engine. Sometimes the buzzing will get quieter or louder when you turn slightly such as when changing lanes.
Tuesday, August 9th, 2011 AT 12:22 AM